Method of manufacturing photoflash lamps



May 16, 1967 Fig}.

R. M. ANDERSON Fig 2.

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METHOD OF MANUFACTURING PHOTOFLASH LAMPS Filed June 29, 1965 2Sheets-Sheet 2 ';;f 29 1 30 l 7 E l i L l 35 6 3/ 3/ 5 t 1 l, J/+4 lnventor: Robertr,M.Ar?e son His AU COTTWeH United States Patent O 3,320,012METHOD OF MANUFACTURDIG PHOTOFLASH LAlVIPS Robert M. Anderson, Euclid,Ohio, assignor to General Electric Company, a corporation of New YorkFiled June 29, 1965, Ser. No. 467,886 Claims. (Cl. SIG-) This inventionrelates to a method or process for producing tubular photofiash lamps.More particularly, it relates to a method for the production of suchlamps which are sealed on one end by an exhaust tip.

It is a constant goal in the photoflash lamp industry to produce eversmaller lamps which will give greater and improved light output. Suchimproved flash lamps are described and claimed in applicants copendingapplication Serial No. 467,831, filed concurrently with the presentapplication and assigned to the same assignee. Such lamps provideincreased internal volume relative to overall external dimensions. Thisis accomplished by changing the geometry of the tipped end of a standardcommercial AG-l photoflash lamp by eliminating the gradual curvature ofthe dome from the lamp bulb to the tip and substituting thereforrelatively straight cylindrical walls that extend out a substantialdistance along the length of the tip and then are sharply turned backinto the bulb in a re-entrant direction to form a retroverted wellsurrounded by a rim. The tip arises from the approximate center of thewell. However, a process was required for the high-speed production ofphotoflash lamps having such a configuration.

Accordingly, it is a principal object of the present invention toprovide a process useful for the production of photoflash lamps having are-entrant dome with a somewhat recessed tip.

Another object is to provide such a process which is capable ofeconomical and highly reproducible utilization on high-speed commercialflash lamp production equipment.

Other objects and advantages of the invention will be apparent from thedescription and the accompanying drawings.

In the drawings:

FIG. 1 is a side elevational view of a flash lamp tube having a baseformed thereon with ignition means and electric contact means in placeand with filamentary combustible material in position for furtherprocessing of the lamp tube blank.

FIG. 2 is a side elevational partly in section of the flash lamp tube ofFIG. 1 being drawn down to form an attenuation or contraction.

FIG. 3 is a side elevational view of the step in the process of theinvention in which the dome is heated and blown out into its desirableconvex shape.

FIG. 4 is a side elevational view of the step in the process of thepresent invention in which the attenuation is pushed into the dome ofthe lamp to form the unique end structure of flash lamps claimed inapplicants abovementioned application Ser. No. 467,831.

FIG. 5 is a side elevational view, partly in section, of the step inwhich the flash lamp bulb is cooled in a bath of liquid nitrogen whileit is exhausted and filled with a combustion-supporting gas.

FIG. 6 is a side elevational view partly in section of the step in whichthe exhaust tip is formed and sealed off by the melting of the glass.

FIG. 7 is a schematic view of a flash lamp prepared according to thepresent invention.

Briefly stated, the present invention in one aspect provides a processfor producing tubular photoflash lamps ice having one end closed by anexhaust tip comprising the steps of:

(A) Heating the lamp tube at the conjuncture of the lamp bulb with theattenuation, (during this step, a gas can be blown into the lamp bulb toround out the top of the lamp bulb, forming a dome),

(B) Allowin the attenuation to cool sufiiciently for it to become rigidenough so that it can maintain its shape while forcing the still hot andplastic inner portions of the conjuncture or dome down into the lampbulb, and

(C) Causing the attenuation and the lamp bulb to move relatively towardeach other to depress the central portions of the conjuncture or dome,forming a re-entrant raised rim surrounding a retroverted well at theend of the lamp bulb.

Subsequent sealing of the lamp by tipping can be done, for example, witha cooled bulb or in a pressurized chamber to make lamps having afill-pressure above atmospheric. Other methods can be used when thefill-pressure is below atmospheric.

In one aspect, the present invention lies in certain manufacturing stepsadded to a process for producing photoflash lamps described and claimedin Patent 3,188,162 Anderson et al., which is assigned to the assigneeof the present invention.

Many details and several steps of the process for producing photoflashlamps according to the present invention are identical to those forproducing prior art AG-l photofiash lamps as described inabove-mentioned Patent 3,188,162Anders0n et al. The steps related to thechanges in the process for the production of improved photofiash lampsas described in above-mentioned Patcopending patent application Ser. No.467,831 Will be particularly described herein. Reference may be made toPatent 3,188,162 for equivalent processes useful in pro ducing standardAG-l lamps.

Referring now to the drawings, FIG. 1 shows a glass lamp tube 1 whichhas already had a stem-press base 2 formed at one end and filamentarycombustible material 7 inserted and compressed in the vicinity of thestem press sealed end. A lamp mount comprising lead wires 4 is sealedthrough the stem press 2. The external ends of the lead wires formelectrical contacts 3, and the lead wires inside the lamp can be held infixed relative position by a glass head 5. The innermost ends of thelead wires are covered with primer ignition material 6, which also is incontact with the flashing filament 35 as shown in the front view of alamp in FIG. 7. The lamp tube is held by an upper holder 8.

As is known in the prior art, lamp tubes can be processed to this stageby sealing lead-in wires into one end of a glass lamp tube to form astem-press base on the lamp tube, with the mount structure havingignition means including a filament wire at its end inside the lamp, andallowing for electrical contact means with its ends outside the lamp.Primer material can then be applied through the open other end of thelamp tube on to a portion of the leaddn wires located within the lamptube so that the primer material contacts the filament Wire. Combustiblematerial may then be introduced through the open end of the lamp tube byany of the several suitable means disclosed by the prior art andpositioned adjacent to the ignition means in the vicinity of the sealedend of the lamp. This prevents the combustible material from beingdeleteriously acted upon by the process of forming and sealing the otherend of the lamp.

FIG. 2 illustrates attenuation 9 separating lamp bulb 19 from thebalance of the lamp tube 13. For this operation, the lower end of thelamp tube 1 which is to form the lamp bulb It may be held by mechanicalmeans or by vacuum means in a lower holder 16. A screen 17 controls theposition of the lamp in holder 16, while vacuum means may be appliedbelow the screen 17 such as through tube 16a. This holder 16 is mountedon a supporting shaft 18 which terminates in a hemispherical bearing 19.The bearing 19 follows cam track 20 at the upper and lower holders 8 and16, with the lam tube being formed, are indexed from one position toanother around a lamp-making machine. Upper and lower holders 8 and 16are rigidly connected together so that the lamp tube 1 can be moved as aunit as the glass is worked.

During the attenuating of the lamp tube, fires a are played on the tubewhile it rotates, as shown by one arrow. These fires 15a coming fromburners 14a causes the tube wall to collapse inwardly somewhat, with thecurvature shown at 12a. After the glass has moved inwardly sufficiently,the lower holder 16 is caused to move downwardly by the configuration oftrack as. the lamp is moved around a lampmaking machine. In this lowerposition, burners 14!; continue to play fires 15b on the tube to formthe desired attenuation, which still must stay open to allow subsequentexhaust and filling of the lamp. This step results in the lamp bulbhaving a gradual curved end 12 from the cylindrical portions of the bulbwall to the conjuncture 11 of the bulb with the contraction 9.

At the next step, as shown in FIG. 3, the lamp is indexed into aposition where burners 23 direct relatively smaller fires 24 on theconjuncture 11 of the bulb 10 at its end 12 with the contraction 9. Thelamp is rotated during this process as shown by the arrow, and a gas isblown into the upper end of the lamp tube 13 such as through a hose 21and connecting plate 22 to cause the end 12 to expand outwardly into aconvexly curved dome. This results in heating the lamp tube at theconjuncture of the lamp bulb with the attenuation, or contraction, 9, asit is referred to. The attenuation 9 is then allowed to coolsufficiently to become rigid enough so that it can maintain its shapeWhile later forcing the still hot and plastic inner portions of thecontraction 9 down into the lamp bulb. Following this step, the lowerholder 16 with the lamp bulb 10 is caused to move upwardly in relationto the upper part of the lamp tube 13 by a rise in the cam track 20 at25. FIG. 4 illustrates the continuation of the rise 25 in cam track 20at 26. When the cam bearing 19 has risen to the upper level of the trackat 26, the lamp bulb 10 will have been pushed upwardly along the commonaxis of the bulb 10 and the tube 13 relative to the then coolerattenuation 9 as illustrated. Of course, any means by which relativemotion of the lamp tube 13 and the lamp bulb 10 toward each other couldbe accomplished would have an equivalent effect. This causes theattenuation 9 to push the center ortion of the dome downwardly to form aretroverted well 27 surrounded by a re-entrant rim 28.

In the next step, the upper end of the lamp tube 13 is gripped in anexhaust-fill apparatus 29 (FIG. 5) which comprises a rubber valve 30actuated by jaws 31. The lamp is exhausted by vacuum means through theexhaustfill head 29 and then filled under a moderate absolute pressurewith oxygen gas. The lamp bulb 10 is then immersed in liquid nitrogen ina trough 36, in order to give a resulting pressure in the finished lampof about 7.5-8 or more atmospheres.

In the tipping operation shown in FIG. 6, sharp flames 33 from burners32 are used to locally melt the attenuation 9 in order to form tip 34.This tip 34 will normally extend slightly above the rim 28, although itsheight from the bottom of well 27 is comparable to that of standard AG-lphotofiash lamps. During this tipping operation, the lamp 10 may, ifdesirable, be removed from the liquid nitrogen bath and held in a holdersuch as that shown at 37 and in transfer mechanism 38 adapted to removethe semifinished lamp bulb 10 from the lamp-making machine on whichthese steps have been performed.

FIG. 7 is a schematic representation of a semifinished lamp ready forthe application of protective plastic coatings to the outside of thebulb. After a holding period to identify leaking lamps, plastic coatingsmay be applied to the lamps for safety purposes. The electrical contacts3 may be bent into any desired shape during, before or after the lampprocessing sequence provided only that the retroverted ends 39 havepreviously been sealed into the lamp base if such a construction isdesired.

While specific examples have been given of the process of the presentinvention, it Will be understood that various changes, omissions andsubstitutions may be made within the spirit and scope of the inventionas defined in the appended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In a process of producing tubular photofiash lamps having one endclosed by an exhaust tip wherein the tip is formed by heating a portionof the lamp tube and drawing it out to form an attenuation through whicha combustion-supporting gas is later introduced into the lamp and theexhaust tip then closed by heating, the steps of:

(A) heating the lamp tube at the conjuncture of the lamp bulb with theattenuation,

(B) allowing the attenuation to cool sutficiently for it to become rigidenough so that it can maintain its shape while forcing the still hot andplastic inner portions of the contraction down into the lamp bulb, and

(C) causing the attenuation and the lamp bulb to move along their commonaxis relatively toward each other to depress the central portions of thecontraction and form a reentrant raised rim surrounding a retrovertedwell at the end of the lamp bulb.

2. In a process of producing tubular photoflash lamps having one endclosed by an exhaust tip wherein the tip is formed by heating a portionof the lamp tube and drawing it out to form an attenuation through whicha combustion-supporting gas is later introduced into the lamp and theexhaust tip then closed by heating, the steps of:

(A) heating the lamp tube at the conjuncture of the lamp bulb with theattenuation while blowing a gas into the lamp bulb to round out the topof the lamp bulb and form a dome,

(B) allowing the attenuation to cool sufiiciently for it to become rigidenough so that it can maintain its shape while forcing the still hot andplastic inner portions of the dome down into the lamp bulb, and

(C) causing the attenuation and the lamp bulb to move along their commonaxis relatively toward each other to depress the central ortions of thedome and form a reentrant rim surrounding a retroverted well at the endof the lamp bulb.

3. In a process for producing a tubular photofiash lamp closed at oneend by an exhaust tip, the steps of:

(A) sealing a lamp-mount structure comprising leadin wires into one endof a glass lamp tube to form a stem-press base thereof, with the mountstructure having ignition means including a filament wire at its endinside the lamp and allowing for electrical contact means with its endsoutside of said lamp,

(B) applying through the open other end of the lamp tube a quantity ofprimer material onto a portion of the lead-in wires located Within thelamp tube so that the primer material contacts the filament wire,

(C) introducing into said lamp tube through said open other end aquantity of combustible material,

(D) positioning the combustible material int-o the portion of the lamptube adjacent to the sealed end,

(E) heating to a plastic condition and attenuating a portion of the lamptube intermediate to the portion containing the combustible material andthe open other end to form an attenuation and to define a lamp bulbwhich is the portion of the lamp tube 4. The process of claim 3 in whichthe tipping off between the stem-press base and the attenuation, of stepI is conducted while the lamp is at low tempera (F) blowing a gas intothe open end of the lamp tube tures materially below room temperature inorder to ob- While heating the conjuncture of the attenuation with taina resulting fill pressure in the finished lamp substanthe lamp bulb toform a convex dome on the lamp, 5 tially above atmospheric.

(G) after the attenuation has cooled to the point of 5. The process ofclaim 4 in which the lamp has been becoming rigid and while the dome ofthe lamp is cooled to the said low temperatures by immersing the stillhot enough to be plastic, moving along their bulb in liquid nitrogen.common axis relatively towards each other the attenuation and the lampbulb so that the open end of 10 References Cited y the Examine! the lampbulb at the contraction takes the form of UNITED STATES PATENTS aretroverted well surrounded by a reentrant raised rim with theattenuation arising from approximately the center of the well,

(H) exhausting the lamp bulb and introducing into it through the openother end a combustion-support- References Cited by the Apphcant inggaseous medium (I) heating and closing by tipping off the contraction736,231 3 /1905 M D lL close to the end of the lamp bulb to hermeticallyseal off the lamp bulb, forming an exhaust tip and RICHARD H. EANES,JR., Primary Examiner. a lamp.

2,956,372 10/1960 Madigan -34 3,113,010 12/1963 Willis 65-108

3. IN A PROCESS FOR PRODUCING A TUBULAR PHOTOFLASH LAMP CLOSED AT ONEEND BY AN EXHAUST TIP, THE STEPS OF: (A) SEALING A LAMP-MOUNT STRUCTURECOMPRISING LEADIN WIRES INTO ONE END OF A GLASS LAMP TUBE TO FORM ASTEM-PRESS BASE THEREOF, WITH THE MOUNT STRUCTURE HAVING IGNITION MEANSINCLUDING A FILAMENT WIRE AT ITS END INSIDE THE LAMP AND ALLOWING FORELECTRICAL CONTACT MEANS WITH ITS ENDS OUTSIDE OF SAID LAMP, (B)APPLYING THROUGH THE OPEN OTHER END OF THE LAMP TUBE A QUANTITY OFPRIMER MATERIAL ONTO A PORTION OF THE LEAD-IN WIRES LOCATED WITHIN THELAMP TUBE SO THAT THE PRIMER MATERIAL CONTACTS THE FILAMENT WIRE, (C)INTRODUCING INTO SAID LAMP TUBE THROUGH SAID OPEN OTHER END A QUANTITYOF COMBUSTIBLE MATERIAL, (D) POSITIONING THE COMBUSTIBLE MATERIAL INTOTHE PORTION OF THE LAMP TUBE ADJACENT TO THE SEALED END, (E) HEATING TOA PLASTIC CONDITION AND ATTENUATING A PORTION OF THE LAMP TUBEINTERMEDIATE TO THE PORTION CONTAINING THE COMBUSTIBLE MATERIAL AND THEOPEN OTHER END TO FORM AN ATTENUATION AND TO DEFINE A LAMP BULB WHICH ISTHE PORTION OF THE LAMP TUBE BETWEEN THE STEM-PRESS BASE AND THEATTENUATION, (F) BLOWING A GAS INTO THE OPEN END OF THE LAMP TUBE WHILEHEATING THE CONJUNCTURE OF THE ATTENUATION WITH THE LAMP BULB TO FORM ACONVEX DOME ON THE LAMP, (G) AFTER THE ATTENUATION HAS COOLED TO THEPOINT OF BECOMING RIGID AND WHILE THE DOME OF THE LAMP IS STILL HOTENOUGH TO BE PLASTIC, MOVING ALONG THEIR COMMON AXIS RELATIVELY TOWARDSEACH OTHER THE ATTENUATION AND THE LAMP BULB SO THAT THE OPEN END OF THELAMP BULB AT THE CONTRACTION TAKES THE FORM OF A RETROVERTED WELLSURROUNDED BY A REENTRANT RAISED RIM WITH THE ATTENUATION ARISING FROMAPPROXIMATELY THE CENTER OF THE WELL, (H) EXHAUSTING THE LAMP BULB ANDINTRODUCING INTO IT THROUGH THE OPEN OTHER END A COMBUSTION-SUPPORTINGGASEOUS MEDIUM, (I) HEATING AND CLOSING BY TIPPING OFF THE CONTRACTIONCLOSE TO THE END OF THE LAMP BULB TO HERMETICALLY SEAL OFF THE LAMPBULB, FORMING AN EXHAUST TIP AND A LAMP.